Motor-control system



H. 0. JAMES.

MOTOR CONTROL SYSTEM.

APPLICATION FILED JAN. 8, I919- IQW lJa

INVENTOR Hen/y Ode/hes.

. ATTORNEY entree STATES I HENRiT D. JAMES, 015 EDGEWOOD PARK,PENNSYLVANIA, 'ASSIGNOR TG WESTING- rarest orrice.

HOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPQRATION F PENNSYL- VANIK.

MOTOR-CONTROL SYSTEM.

neeaeae.

To all whom it may concern:

Be it known that l, HENRY D. JAMES, a citizen of the United States, anda resident of Edgewood Park, in the county of Allegheny and State ofPennsylvania, have invented a new and useful Improvement inMotor-Control Systems, of which the following is a specification.

invention relates to motor-control systems and has particular relationto motoraccelerating systems embodying resistorcontrolling contactors,the closing of which is under the control of successively operablerelays.

in previously proposed systems of this character, the relay coils areenergized by the motor current to automatically maintain the relays openfor a predetermined length of time, or so long as the current is above apredetermined value, after every operation of short-circuiting a portionof the accelerating resistor. As the motor current rises from acomparatively low to a comparatively high value aftereveryshort-circuiting operation, these systems are subject to thedisadvantage that the relays may close prematurely, before themotor'current can build up to values sufficiently large to hold themopen. '20 make these systems at all practical, it is necessaryto-mechanicallv interlock the contactors and the relays and to provideadditional means for maintaining the relays open until the currentbuilds up to the required holding values.

An object of my invention is to provide an accelerating system of theabove designated character, the relay coils of which shall. bev

. responsive to uniformly decreasing electrical conditions so that themechanical interlocking means and the additional maintaining means maybe dispensed with.

Another object of my invention is to provide such a system which shallbe especially adapted for push-button control.

A further object of my invention is to provide a control system for amotor, the acceleration of which shall be determined in accordance withseveral difi'erent methods Still another object of my invention is toprovide a motor-accelerating system which shall be adapted to controlalso the speed of the motor.

Specification of Letters Patent.

relay coils are made Patented Sept. 27, 1921;

Application filed January 8, 1.919. Serial No. 270,146.

Other objects of my invention will appear hereinafter.

According to the specific forms of my invention herein illustrated anddescribed, the responsive to the drop 1n the voltage across theaccelerating resistor, but if an alternating-current motor be employed,they may be energized by the.

The startthough this opening may be before or after the motor cirdrop involtage across two-phase leads. relays are automatically opened beforeing the motor, efiected either cuit is closed,

ccordi'ng to one form of my lnvention, the motor acceleration iscontrolled both by the voltage drop across the resistor and thecounter-electromotive force of the armature. According to another formof my invention, t e control circuits are so arranged as to control notonly the initial acceleration of the motor but also its accelerationafter speed changes.

In the accompanying drawings, Figure l is adiagrammatic representationof circuits and apparatus for carrying out my invention; Fig. 2 is asimilar diagram, the circuits being arranged for control of the motorboth in accordance with the drop in voltage across the resistor and thecounter-electromotive force of the armature, and Fig. 3 is adiagrammatic view of a system illustrating the application of myinvention to an alternating-current motor.

Referring to Fig. 1, a direct-current m0-.

tor, the armature of which is shown at l and the shunt field-magnetwinding at 2, is connected between line conductors 3 and 4, separated bya line contactor 5, with a regulating resistor 6 normally in series withthe armature l. The contactor is adapted to be closed by an energizingcoil 8. One or more contactors 10, ll and 12 (three are illustrated)control the shunting of successive portions 13, 14c and 15 of theregulating resistor 6 through the medium of energizing coils 19, and 21,the circuits of which are controlled by normally closed relays 25, 26and 27 having energizing coils 22 22 and 22, respectively, connected inparallel (F ig. l or in series (Fig. 2) across the regulating resistor6. The relay is adapted to close auxiliary contact members 60 whenoccupying its open position. Switches 51 and 61 or simultaneouslytherewith.-

are mechanically connected to the contactor so as to be opened andclosed simultaneously with the opening and the closing of the contactor.The control circuits are adapted to be energized by a start push buttonand to be denergized by a stop push button.

Upon closing the start pushbutton, a circuit is established from theline conductor 4, through the stop-and-start push buttons, a conductor28, the coils 22, 22 and 22 and the armature 1, to the line conductor 3.This circuit is of high resistance, the resistance being embodied in thecoils 22, 22 and 22, or an additional resistormay be employed. Thecurrent which passes through this circuit will, therefore, not be ofsufficient strength to have any appreciable effect upon the motorarmature 1, but the relays 25, 26 and 27 will be immediately opened. Theopening of the relay 25 causes the closing of a circuit which extendsfrom the line conductor 1, through the stop-andstart push buttons, theconductor 28, and the contact members 60 and the coil 8, by way of aconductor 30, to the line conductor 3. The consequent energization ofthe coil 8 causes the closing of the line contacto'r 5 and themechanicallyuconnected switches 51 and 61. The cont-actor 5 establishesthe motor circuit. The switch 61 creates a holding circuit for the coil8 through the stop push button. The coil 8 will thus remain energized tomaintain the contactor 5 and the switches 51 and 61 closed, even thoughcontact be broken at 60. The switch 51 creates a holding circuit for thecoils 22, 22 and 22 in shunt to the start button so that this button maybe released, the circuit. of the coils 22, 22 and 22 bein made from theline conductor 4, through tie stop push but ton, the switch 51, theconductor 28, the relay coils and the armature 1, to the line conductor3.

Upon the establishing of the motor circuit, the coils 22, 22 and 22 wilbe energized in accordance with the drop in voltage across the resistor6. As'the motor begins to accelerate, and the current flowing throughthe motor to decrease, in conseuence, the voltage across the resistorwill ecrease and, assuming the relays 25, 26 and 27 to be properly,des1gned,-as by making them of difierent weights or by causing them tobe actuated by springs of different strengths or by properl designingthe number of turns in the coi s 22, 22 and 22,-'- so as to cause theserelays to close in succession in accordance with different values of thevoltage across the resistor 6, the relay 25 will close first,establishing a circuit extending from the line conductor 4, throu h thecontactor 5, a conductor 29, the relay 5 and the coil 19, by way ofa-conductor 30, to the line conductor 3. 4 The consequent energizetionof my system mes es tion of the coil 19 causes the contactor 10 to closeand the resistor portion 13 to be ShOI'tr. circuited. In similarfashion, the relays 26 and 27 will close later, in accordance with thesuccessively lowered values of the voltage across the resistor 6, andthe coils 20 and 21 will become energized to cause the closing of thecontactors 11 and 12 and the consequent short-circuiting of the portions14 and 15 of the resistor 6. The armature 1 will then be connecteddirectly across the line.

A study of the system just described will make clear that it isimpossible to start the motor unless the resistor 6 is initially incircuit with the armature 1, thereby reventing injury to the motor whichwould result if the armature 1 were initially connected directly to theline conductors 3 and 4:. This result is made possible b the fact thatthe line contactor 5 cannot close'the motor circuit until the relays 25,26 and 27 have reviously been opened to prevent the closing of thecontactors 10, 11 an d,12 by their energizing coils 19, 20 and 2,1, andthe consequent short-circuiting of the resistor 6. It is only when therelay 25 occupies its open position, to close the contact members 60,that the coil 8 can be energized to cause the closing of the contactor5.

it is not, however; essential to the operathat the relays 25, 26 and 27be 0 ened before the contactor' 5 is closed. 11 Fig. 2, I- haveillustrated a system in which the contactor 5 ma be closed before, orsimultaneously with, t e opening of the relays, but, of course, themotor is not permitted to start until the relays 25, 26 and 27 havefirst been opened. In the system of Fig. 2, 1 illustrate an additionalfeature of control which may, if desired, be embodied also in the systemof Fig. 1.

The arrangement of circuits is similar to that of Fig. 1, except thatthe coils 19, 20 and 21 are each connected, at one end, to theconnecting points of the successive resistor portions 13, 14 and 15,and, at the other ends, by way of the conductor 30, to the other side ofthe armature 1. The coils 19, 20 and 21 are therefore responsive to thecounter-electromotive force of the armature.

Upon the actuation of the start push button, a circuit is establishedwhich extends from the line conductor 1, through the two push buttonsand dividin rent passes through the coils 22, 22 and 22, the resistor 59and he armature 1, and the other part passes through the coil. 8, by wayof the conductor 30, the two branches of the circuit terminating in theline conductor 3. The relays 25, 26 and 27 are immediately 0 ened andthe contactor 5 is immediately 0 osed. It is not necessary, however,that the relays be immediately opened, because,

, part of the curshown. The switch motive force of length of time, theycannot eflect the operation of the motor, since the coils 19, 20 and 21cannot actuate the contactors 10, 11 and 12 until thecounter-electromotive force of the motor builds up to a sufficientlyhigh value. It is safer, however, tohave the relays and the contactor 5operate together, as 61 establishes holding circuits for the coil 8 andthe relay coils, but the switch 51, in this case, controls the circuitsof the coils 19, 20 and 21 across the armatur terminals.

- The relays 25, 26 and 27 are arranged to be successively closed inaccordance with the value of the fallin voltage drop across the resistor6. Upon t e closing of the relay 25, a circuit is established from oneside of the armature 1, "by way of the conductor 30, through the switch51, to the other terminal of th armature 1. Similarly, upon the closingof the relays 26 and 27, the coils 20 and 21 will be energized by thecounter-electrothe motor, the circuit of the coil 20 including theresistor portion 15.

When this counter-electromotive force, therefore, becomes .great enoughto energize the coils 19, 20 and 21 sufi iciently to cause the closingof the contactors 10, 11 and 12, the resistor portions 13, 1e and 15will be successively short-circuited.

In the illustrated embodiment of this invention, the coils l9 and 20 areshown as controlled not only in accordance with thecounter-electromotive force of the motor, but also in accordance withthe resistance through the resistor portions 14, and 15, respectively.If desired, of course, the circults may be so arranged as to close thecontactors 10, 11 and 12 in reverse order so as to short-circuit theresistor portions 15, 14

and 13, in the order named, in which event 11 and 10 will be succesthecontactors 12,

' in accordance with the sively controlled counter-electromotive forceof the motor only..

The acceleration of the system of Fig. 2 '5 thus controlled inaccordance with two different methods of control. First, the relays 25,26 and 27 are successively'closed in accordance with the drop inpotential across the resistor 6; secondly, it is immaterial when theserelays are closed if the counter-electromotive force of the motor hasnot previously built up to values sufiiciently large to control thecontactors 10, 11 and 12. If this counter-electromotive force builds uptoo rapidly, the closing of the contactors must await the closing of therelays in accordance with the voltage drop across the resistor. If thisvoltage drops too rapidly, the closing of the contactors must await thebuilding up of the counter electromotive force. As shown, moreover, theaction of the coils 19 and 20 is delayed by the resistor portions 14 and15.

I have shown the coilsf22, 22 and 22, in

they may both Figs. 1 and 2, as connected across the entire resistor 6.It will be connected across a smaller port on or across differentportions of this resistor.

into two resistor portions .13, 13, 141-, 14 and 15, 15, respectively,which are adapted to be controlled by and 71, having energizing coils19, 20, 21, 72 and '73, respectively. The contactors are respectivelycontrolled by relays 25, 26, 27, 68 and 69, having energizing coils 2222*, 22, 22 and 22 which are connected, in series or in parallel, inseries with a resistor 59 of high resistance, across two of the phaseleads of the secondary winding 66. lit is, of course, possible, asillustrated in Fig. 7 of No. 236,937, filed May 27, .1918, to connectthese relay coils directly across the terminals of-the resistor, as inFigs. 1 and 2, but 1 preferably connect these coils as shown becausethey will thus, as in the case ofthe other connection, be subjected to afalling voltage and because, by means of this con nection, it ispossible not only to control the acceleration of the motor but also itsspeed. This is because a high-resistance coil, connected across two ofthe leads of the secondary winding of an alternatingcurrent motor,yields a decreasing magnetic field as the motor speed increases. The contactor coils 19, 20, 21, 72 and 73 are connected, respectively, incircuit with the relays and the master switch 7, by conductors theprimary leads. A

78 and 79, to two of slow-acting relay 80, having an actuating coil 81in the circuit of one of the second ary leads, is connected in thecircuit of the conductor 79 for an obvious purpose.

The operation is as operation of the master switch 7 to its firstoperatire position, the coil 8 is energized to cause the closing or" thecontactor 5, thereby to connect the primar winding 65 to the source ofenergy. he motor is thereupon energized, but current cannot yet flowthrough the contactor coils, by way of the conductors 78 and 79, eventhough the master switch 7 be immediately actuated to be obvious that ofa master contactors l0, 11, 12,

my copending application, Serial succeeding positions, because the relay80 is open. Current is induced in the secondary winding 66 and traversesthe resistor 6.

' The relay coils are energized, causing the opening of the relays.After a time, the slow-acting relay 80 is closed by the coil 81 so that,when the relay) 25 is first closed, upon the voltage drop etween thesecondary a circuit is established, assuming the master switch 7 .tooccupy its second position, from one of the primary leads, by theconductor 78, through the relay 25 the coil 19, the master switch 7, theconductor 79 and the slow-acting relay 80, to a second of theprimaryleads. The contactor 10 is thereupon closed by its coil 19 toshort-circuit the resistor portion 13. Upon the voltage differencebetween the secondarg leads alling to a second and lower pre eterminedvalue, the relay 26 will become closed to cause the closing of thecircuit of the coil 20, when the master switch 7 is moved to its thirdposition. The consequent closing of the contactor 11 results in placingthe resistor portions 14 and 15 in parallel to each other and in serieswith the resistor portion 13, thus again reducing the resistances of theseveral circuits of the secondary phase windings. Upon the relay 27later closing, the contactor 12 will become closed to shortcircuit theresistor portions 13, 1 1 and 15. Similarly, the closing of the relay 68will cause the closing of the contactor 70 to place the resistorportions 14: and 15 in parallel and, ultimately, the closing will causethe closing of to short-circuit the 15. The resistor the contactor 71resistor portions 14 and 6 will now be entirely short-circuited. Theslow-acting relayl remains closed until after all the relays ave closedflnthis system, too, it is necessary that the resistor 6 be traversed bycurrent before the starting of the motor; for, unless this is so, thecoil 81 will and the above-described operations can not take place.

It will be noted that an additional advantage accruing from theconnection 0 the relay coils across two of the secondary leads is thatit renders possible the employment of an unbalanced secondary resistor.

A further advantage is the following: the relays may be made to open andto close at a difference in voltage of from 10 to 15 per cent. Bysuitably manipulating the master switch 7 the circuits of the contactorcoils may be opened for purposes of speed control. Upon the consequentreinsertion of resistance into the secondary circuit of the motor, themotor speed will-decrease, thereby causing'several or all of the relaycoils to reactuate their relays to their open positions, which relayswill again close, in

leads falling to a predetermined value,

that my invention of the relay 69' 0 opening said not be suiiiciently.energized,-

source 0 energy for said ling said short-circu'r jting. switches,

accordance with speed conditions, upon the master switch 7 being againactuated to close the circuits of the contactor coils. The danger ofsuddenly throwing the motor directly across the line, without protectiveresistance, is thus avoided.

I have illustrated but three of the many forms which my invention maytake and have suggested a few others. It is obvious is not limited tothe specific embodiments therefore, that my claims be construed broadly,except in so far as limitations may be specifically set forth therein.

1 claim as my invention:

1. The combination with an electric motor having a resistor associatedtherewith, a switch for controlling said resistor and a normally closedrelay for controlling said resistor-controlling switch, of a coilenergized in accordance with the voltage across said resistor forcontrolling said relay.

2. The combination with an electric motor having a resistor associatedtherewith, a switch for controlling. said resistor and a normally closedrelay for controlling said resistor-controlling ed to be subjected to adecreasing voltage for controlling said relay and means for opening saidrelay .preliminarily to shortcircuiting said resistor.

3. The combination with an electric motor having a resistor associatedtherewith, a plurality of switches for short-circuiting said resistorand a normally closed relay for controlling each of said short-circuitsing switches, said relays being adapted to be successively closed inaccordance with predetermined conditions, of means for relays beforestarting said motor.

4. The combination with an electric moto;- having a resistor associatedtherewith, a source of energy for said motor, a switch forSllOlt-OlI'CllltlIig said resistor and a relay ;tor controlling saidswitch, of a coil energized in accordance with the voltage across saidresistor for controllin said relay and means for connecting said coil tosaid source before starting said motor.

5. The combination with anelectric motor havin motor, a plu- -circuitinsaid regressive y acays for controlrality of switches'ior shor resistorand a plurality of t'iated, normally closed re ing an energizing toil,of means for connecting said coils to said source before startin saidmotor, and means for thereafter su jecting said coils to the voltagedrop of said resistor.

6. The combination with an electric motor having a resistor associatedtherewith, of a switch controlled in accordance with the shown and Idesire,

switch, of a coil adapta resistor associated therewith, a

each havvalue of the counter electromotive force troinotive force ofsaid motor for contro1- 10 of said Inotor for controlling said resistor,

ling said resistor and a swltch controlled and a switch controlled 1naccordance with by the voltage of said resistor for controltheelectrical conditions of said motor for lin saidcounter-electromotive-force switch. controlling saidcounter-electromotive-force fn testimony whereof I have hereunto switch.subscribed my namethis 24th day of Dec, 15

7. The combination with an electric mo- 1918. tor having a-resistorassociated therewith,

of a switch controlled by the counter-elec- HENRY D. JAMES.

